Signaling system



T. A. MOLLARD SIGNALING SYS TEM Jan.

Filed May 19. 1923 2 ShgetS-Sheet 2 /1 //"e/'lrzoup/es W40-LX 4/ l) ZE N/NVE/voe 7.74. Mo//araf /wg/vfss. l ma@ Afro/@NE V5.

Patented Jan. 11, 1927.

lUNITED STATES 1,613,802 PATENT OFFICE.

THOMASA AIMOLLARD, OF OAKLAND, CALIFORNIA, ASSIGNOR T PACIFIC FIRE EX-TINGUISHER CO., O F SAN FRANCISCO, CALIFORNIA, A CORPORATION OF 'CALI-FORNIA.

SIGNALING SYSTEM.

Application led May 19,

This invention relates to a signaling system, and more particularly to asystem in which a plurality of signals may be independentlytransmittedand may be caused to affect independent receiving circuits. Ihave developed such a system for use with certain types of fireprevention circuits, but as Will become apparent from the followingdescription, the broad features of my invention may be applied to a widevariety of signaling circuits.

It is thus one of the objects of my invention to provide a signalingcircuit for a plurality of signals that may be separatelylggitransmitted and received by proper selective devices.

` In order to effect this result, I utilize signaling currents .ofradically different char- 1. acteritics so that the same path may beused by them WithoutV substantial interference.

Thus in those embodiments I shall describe, -I utilize a normally closedcircuit for signaling by -direct current, the signaling being performedby opening the circuit one or more -times in succession or in a definitesequence. I make use of the same closed circuit, or a part thereof, as aportion of another circuit for sending alternating or periodic currentsignals. In the broader aspects of my invention, it is possible to useperiodic currents for both signals, provided they employ frequencies ofsuch relative value: that each of the selective devices receiving thesignaling impulses may be arxranged to exclude substantially all of thecurrent transmitting the other signal, as by the aid of inductances andcapacities. It is thus another object of my invention to provide aclosed circuit over which tWo separate signals may be sent, one byinterrupting the circuit in a predetermined order, and the other bytransmitting over at least a portion of it, a current havingsubstantially no ef-A fect upon the devices for receiving the othersignal. Y

My invention is especially applicable for certain typesof automatic firealarm signals, in :which some form of temperature responsive element,such as a thermostat or a. thermocouple, is arranged to operate thealarm upon the product-ion of abnormal temperature effects. Such thermalresponsive elements may be appropriately located in buildings or'otherplaces where the protection is desired, It is usual in such systems toar'- 1923. Serial No. 640,070. i

range a circuit thatU is rendered active by these elements to operatethat street lire alarm boxwhich is nearest the scene of install-ation ofthe thermal responsive elements, .so that the lire department may besummoned, in a manner entirely similar to a manual operation of the,alarm box. The circuit over which the alarm box sends signals is aclosed one, and includes al sourcev of direct current. The signals aresent by interrupting the circuit in a predetermined'order,` as by theuse ofa code wheel operating a contact in'the fire alarm box. The closedcircuit includes all of the irealarm boxes in their various locations,so that the one` closed circuit serves for the transmission of signalsfrom any` point. Furthermore such .an arrangement has the additionaladvantageA that the whole circuit is under test; that is, an accidentalbreak in the circuit is immediately brought to the attention of the firedepartment, since the station receivers are ymade to respond to theopening of this circuit.

In order to ensure that the circuits associated with the thermalresponsive elements are in proper Working order and capable of givingprotection, it has been proposed so to arrange these circuits that anyaccidental derangement, such as a break in a i5 Wire, would also serveto operate the fire v alarm box with which the protection s stem isassociated, even if there is no lire. t was intended that suchderangement of the circuit would thus call the attention of the vfiredepartment to these conditions. However, such an arrangement is notonlyannoying, but also disadvantageous in other ways. Although a separate,distinguishable code is sent for the trouble signal, still it ties upthe series circuit, and thus a true fire alarm in another vicinity,simultaneously turned in, would pass unnoticed at the central station,or else be materially delayed, because ofthe prior open-circuiting ofthe series alarm box 100 circuit by the occurrence of trouble in thethermal responsive protective system. It is another object of myinvention to correct such conditions, and to make it possible tovreceive at the central station, simultaneously 106 and withoutinterference, both a true fire alarm, and a trouble signal at the siteof the installation of the thermal responsive devlces. f y

The occurrence of trouble in the auto- 11'.

matic lire protection circuits, is so arranged in my invention that 1tleaves the series d1- rect current fire alarm system intact, but 1nsteaduse is made of this circuit .to ltransmit alternating current signals ofa' predetermined character. These alternating current signals operate,upon a proper form of signaling device at the fire station and serve toapprise the station that there 1s some trouble with the circuits. Thetrouble may then be corrected by those whose duty it is, upon theirattention being called to `these conditions bythe fire department.

My invention possessesother advantageous features, some of which withthe foregoing, will be set forth at length in the following description,where I shall outline in full those forms of the invention which I haveselected for illustration in the vdrawings accompanying and forming apart of the present specification. Although I have shown in the drawingsonly a few forms of my invention, I do not desire to be limited to them,since the invention as expressed in the claims may be embodied in otherforms also.

Referring to the drawings:

Figure 1 illustrates in a diagrammatic manner, the broad features of myinvention;

Fig. 2 is a more detailed wiring diagram of my invention as applied. toan automatic tire alarm system; and

Fig. 3 is a wiring diagram ofthe receiving apparatus that may be used inconjunction with the arrangement of Fig. 2.

l In Fig. 1, I illustrate my invention as applied to any form ofnormally closed signallng circuit, including the source 11, and leads 12and 13. There is a completelyclo'sed circuit including this source andthe leads, as well as one or more signaltransmitters 14 and a relay coil15. The transmitters 14 may be caused to operate to open this closedcircuit in a definite sequence, and the relay 15 will drop its armature16 in the same sequence. Thus for example one of the transmitters 14 maybe arranged to open the circuit once and to close it again, whileanother may 'be arranged to open the circuit twice. The numwheelsarranged to ber of such transmitters may be multiplied to any desiredextent, and under such circumstances, they may be'provided with codetransmitting devices, to cause interruptions of the circuit to transmittwo or more separated series of signals. Thus if one transmitter 14 isassociated with the number 251, for example, it will be arranged tointerrupt the circuit twice, then after an appreciable interval of rest,lve times, and' after another rest interval, once. These signals may bemost conveniently transmitted by code be rotated by any approprlatesource of power, such as a spring motor for lnstance.

The relay coil 15, in dropping its armature 16.` completes a localcircuit forcncrizinfr an alarm signal 17, such as a lamp, gell, buzzer,or a tape recorder. From the sequence of o eration of this localcircuit, it is ascertaine which one of the transmitters 14 has beenactuated. This system as thus far described is substantially that whichis in common use for turning in lire alarms, the transmitters 14 beingin that case alarm boxes situated on the streets of the protection area.

My invention contemplates the use of the system for transmitting signalswhich do not affect the alarm 17, but which do affect another device 18.For this purpose a source of current 19 is utilized, which has afrequency characteristic materially different from that of source 11.For example, source 11 may be a direct current source, or in general, alow frequency source; while source 19 may be of materially higherperiodicity. This source 19 is connected between the condensers 20 and21 bridged across the leads 12 and 13 near the place where these A. C.signals are to be propagated. A pair of condensers 22 and 23 aresimilarly bridged across the leads 12 and 13 near the place where the A.C. signals are to be received. Between these condensers the signalresponsive device 18 is connected. A connection 24, which m'ay be theearth, serves to complete the A. C. circuit through transmitter 25 andthe source 19. The A. C. signaling circuit may the`n be traced asfollows: from the source 19 to the point 26, where the circuit branches,one branch including condenser 20, line 12, and condenser 22, and theother branch including condenser 21, line 13, and condenser 23; thebranch circuits reunite at point 27, through the device 18, connection24, transmitter 25 and source 19. Substantially none of the alternatingcurrent can ilow through the direct current signaling relay 15, sinceboth leads 12 and 13 are operated in parallel for the A. C. signal.Furthermore eondensers 20, 21, 22 and 23 prevent the flow of direct orlow frequency current through the signaling device 18. It is thusevident that the two kinds of signals do not interfere with eachother,even if transmitted at the same time. Various modiiicat-ions may also beresorted to, the arrangement being merely diagrammatic.

As mentioned hereinbefore, this principle may be utilized with firealarm systems, where the periodic current signal may be turned inwhenever there is something wrong with an automatic alarm circuit havingthermal responsive elements. Fig. 2 illustrates in a more elaboratefashion one adaptation ot the invention for such a purpose, In thisfigure I indicate but one lire alarm box 28, the outline of which isshown in dotted lines', but of course it is to be understood that the 29and 30, may include as many of these or low frequency current source 31,as illustrated in Fig. 3. In' the present instance this circuit operatessubstantially as that illus- -trated in Fig. l; that is, upon theoccurrence ot an open circuit through the alarm boxes 28, the relay 32causes a current to flow through a signaling device 33.

I have also indicated, in a purely diagrammatic manner, one form ofmechanism in the box 28 that serves to transmit the tire alarm signals.A code wheel 33 having projections on its periphery is so arranged withrespect to the spring contacts 34, that its rotation first causes one ofthe projections on the wheel to move away from the-contacts and permitsthem to open. Continued rotation of the wheel 33 will obviously causethe contacts to be made and broken in succession Ain a predeterminedorder dependent upon the particular arrangement of the pro-- jections.The wheel 33 may be rotated by any appropriate mechanism, as for examplea spring motor 35, and may be normally restrained by the. aid ot a pawl36. *To release the pawl for turning in an alarm, a lever 37 isprovided, which when operated permits the spring motor 35 to rotate. The

operationof this lever may be manual, or

as in the system illustrated, may be effected automatically in responseto dangerous temperature conditions in a locality which is in electricalconnection With the mechanism of the box 28. One form of such anautomatic arrangement is illustrated, in which the electromagnet 38,when strongly enough energized, serves to trip the levier 37, by the aidwith each other. A small battery 41, serves' to. furnish a minutecurrent to this close-d circuit. For this purpose a pair of resistauces138 and 139 are connected across the battery 41, and leading from theends ot one ot' these resistances are wires 140 and 141, which connectthe therinocouples inseries with a current responsive element or Contactmaking galvanometer 42. This galvancmetei' is so arranged that undernormal circunistances, it is in a neutral posit-ion as shownv betweentwo contacts 43 and 44. The small battery 41 (usually a single cell)furnishes just enough current to the circuit in shunt to resistance 139to keep the contact making arm 45 in this central position, by approisincreased materially.

priate adjustment of -these resistances. l'Vhen, however, there isadangerous temperature rise, one or more of the thermocouples create asufficient E. M. F. to cause the contact arm 45 to move to the left andmake contact with the point 43. This movcment serves to cause strongenergization ot the actuating electromagnet 38, b the aid ol'` certaincircuits now to be dcscri ed. The same result may be manuallyaccomplished, if desired to turn in an alarm. by short circuiting theresistance 138, as by aid of the switch 142.

The relay 46 is so arranged that While arm 45I is iu the neutralposition, a weak current only flows through it., which is insuicicnt tocause its armature 47 to be attracted to make contact with point 48. Thecircuit for this relay may then be traced as follows: from battery 49,relay 46, contact arm'45, relay 50 ot relatively high resistance', (thepurpose of which will be hereinafter explained), resistance 51, battery52 and back to battery 49. When', however, the contact arm 45 touchescontact 43, the circuit may be traced as follows: from battery 49, relay4 6, Contact arm 45,- contact 43, back to battery 49. Thus theresistances represented. by the coils of relay 50 and the resistor 51are shunted out of the circuit, together with battery 52. The net resultis, by proper dey sign, that the current iiow through'relay 49 The relayarm 47 is attracted, and contact made bet-Ween it and the point 48.

The completion of this circuit in turn causes a strong energization ofthe electromagnet 38 by acting directly upon the circuit whichv includesthis electromagnet. Even when the contact is broken between armature 47and contact 48, a Weak current flows through the coils 38 so as to placethis circuit under test. This Weak current is insuicient to operate theelectromagnet, but it is sufficient to maintain certain other troublecontacts in a definite relation. Should this circuit become inoperative,so that the weak current is interrupted, these trouble contacts causethe transmission of 'Inn a signalv to the re station. i I Shall later onthere is neither' a tire nor any circuit dis- 20 turbance. The batteries49 and 52 serve to provide in this instance the necessary electricalenergy for operating substantially all ot the circuits. When there isneither a 'fire nor trouble, the circuit'for the electromagnet 38 may betraced as follows: from' the right hand terminal of the battery 52,connections 54 and 55, adjust-able resistance 56', armature 57 of relay50, contact58, connection 59, relay coils 68, a pair of spring contacts60 normally in engagement, connections 61 and 87, a secondary coil 62 ona core 63, connections 66 and 67, a pair of contacts 53 that aremaintained in closed condition by the wheel 139 until the transmissionof a lire alarm, connections 69, 70 and 71, electromagnet 38, a pair ofcontacts 141 operated similarly to contacts 53, connections 72 and 73 tothe left hand terminal of battery 49, through this battery andback tobattery 52. This circuit as traced includes the sources 49 and 52, asWell as the resistance element 56 and the relay 68, and the currenttherethrough, while sutlicient to operate relay 68, is insufficient tooperate the electromagnet 38. However, upon closing of contact betweenarmature 47 and point 48 of relay 46, in response to a dangerous rise intemperature, or in responfe to the shorting of resistance 138 by switch142, the resistance 56 is shunted out of this circuit, as Well as relaycoils 68, and the rcsultant strong energization of magnet 38 issuiicient to cause operation of the mechanism in the alarm box 28. Thecircuit may now be traced as follows: from the right hand terminal ofbattery 52, connections 54 and 55, armature-47, contact 48, connection67, contacts 53, connections 69, 70, 71, electromagnet 38, contacts 141,connections 72 and 73 to theleft hand terminal of battery 49, throughthis battery and back to battery 52.

Should the thermocouple circuit be inoperative for any reason, thearrangement is such that relay 68 becomes deenergized, and drops itsarmature 74. The dropping ot this armature sets into operation signaltransmitting devices which do not in any Way alter the main fire alarmcircuit including the leads 29, 30, and the transmitter boxes 28, northe control circuits therefor which have just been traced. This isaccomplished by causing the relay 50 to drop its armature 57. It is tobe noted that the contacts controlled by this relay are in circuit withthe electromagnet 38 and relay 68, While relay 46 is inactive, so thatif the armature 57 drops, the relay 68 becomes open circuited, and thesignaling devices controlled thereby are set into operation. NormallyWhile the arm 45 of the contact making galvanometer 42 is in neutralposition, the relay is energized from both batteries 49 and 52, throughresistance 51 and the coils of relay 46. This energizing circuit hasbeen traced heretofore, and it is therefore not essential to repeatit.Upon the occurrence of trouble in the thermocouple circuit, which causesit to become inoperative, the galvanometer 42 becomes entirelydeenergized, and the arm is retracted to the right; contact is thenestablished between it and the stationary contact 44. Vhen this occurs,the relay coils are shunted by the contacts, and the relay drops itsarmature. The status of relay 46 is unchanged, since resistance 51 isstill in circuit with the batteries 49 and 52, and the resultant currentflow is still too weak to cause a raising of armature 47. The circuit'under these circumstances may be traced as follows: from battery 49,relay 46, arm 45, contact 44, 'resistance 51, and battery 52 back to thebattery 49.

The relay 68 becomes inactive not only upon the occurrence of trouble inthe thermocouple circuits, but also upon the occurrence of any improperopen circuiting of the circuit for electromagnet 38. It is to be notedthat this circuit, which is thus put under test purposely includes inseries all of the connections that are useful in the automatictransmission of a tire alarm, and also, as will be evident later on, theimportant connections which serve to transmit the periodic currenttrouble signal. There is thus a strong assurance that any breaking ofthe wires, exhaustion of battery 52, or any other accidental happeningthat would destroy the utility of the system, will cause thetransmission o an alternating current signal to the fire station.

The trouble signal may be transmitted by the aid of a code Wheel 75,which may be entirely similar to the code Wheel 33. A pawl or detent 76is released upon the dropping of armature 74 which permits thecontinuous rotation of code Wheel 75 until the spring motor 77 iscompletely run down. The spring contacts 78 operated by the code Wheelare under normal circumstances open, and are closed and opened by thecode Wheel in succession as it revolves. These contacts control a sourceyof periodic current. In the present instance this current isconveniently generated by the aid of an induction coil having a primaryWinding 79 and a secondary Winding 62, which has been mentionedhereinbefore as being in the test circuit of electromagnet 38. Avibratory contact arrangement 80 is provided in the Well understoodmanner for rapidly making and breaking the circuit through this primarycoil 79 and a source of current, whereby the core 63 Will be subjectedto a rapidly varying magnetizing force. The batteries 49 and 52 areutilized to energize the coil 79, and the circuit for this purpose, Whencontacts 73 and 80 are completed, may be tra-ced as follows: from theright hand terminal of thc battery 52, connection 54, contacts 78, con--tact/s 80, coil 79, connection 73 to the left. hand terminal yof battery49, through this battery back to battery 52. Of course during the periodwhen' a code Wheel projection connects the contacts 78, the circuit justtraced is made and broken a very large number of times by the aid of thevibratory contacts 8O in a well understood manner;

thus during the intervals of closure of contacts 78, a train of currentwaves is generated in the secondary coil 62 in inductive relation withthe primary 79. It is to be noted that signaling impulses would betransmitted even if the contacts 80 should stick for any reason. Under-such circumstances the making and breaking of the circuit through coil79 would be accomplished solely by contacts 78 and the rojections of thecode wheel 75. This ma e and break serves alternately to establish andto destroy the ux in core 63, and thus to generate an impulse E. M. F.in the secondary 62 at those times. The dropping of armature 74 of thetest relay 68 also causes the contacts 60 to become separated. Thisserves to interrupt a circuit which would otherwise shunt some of theenergy developed in the secondary coil 62 through the batteries 49 and52; this circuit may be traced as follows: from the right hand terminalof coil 62, connections 87, 61, contacts 60, coils 68, connection 59,contact 58, armature 57, resistance 56, connections 55, 54, batteries52, 49, connection 73, and condenser 81 to the left hand terminal ofcoil 62. The opening of this circuit also in terrupts the test circuit,including coils 68 and magnet 38.

The secondarycoil 62 is so connected, with respect to the lire alarmcircuit wires 29 and 30, that the periodic current produced thereinflows through these Wires in parallel to affect certain currentresponsive signaling devices at the fire station. Direct current signalsproduced b the main lire alarm mechanism cannot ow in these devices dueto the insertion of condensers in the periodic current. circuit, and inthis way it is also possible, as pointed out in connection with Fig. l,to prevent interference with the operation of the series direct currentfire alarm circuit. rl`he periodic current circuit at the transmittingend may be traced as follows: from the left hand terminal of secondary62, condenser 81, connection 72, contacts 141, electromaguet 88,connections 71xand 7() to the cent-ral point of the condensers 82 and 83bridged across the wires 29 and 30. The current then is transmitted overthe wires 29 and 32 in parallel to the fire station. The periodiccurrent flowing through the electromagnet 38 is of such a nature that itdoes not affect its actuation, since it is a direct current magnet. Atmost it may cause the magnet to chatter a little. In order to ensure thetransmission of the periodic current signal even if this path may fail,another path is offered from the secondary 62 to the condensers 82 and83, which may be traced as follows: from the left hand terminal of coil62,.

connections 66 and 67, contacts 53, and connection 69 to the condensers82 and 83. The return for the coil 62 from the fire station may beeffected in any desired manner; in

the present instance grounded connections are used both at thetransmitting and receiving end to accomplish this result. For this`purpose the right hand terminal of coil 62 is grounded at 85 throughthe condenser 86 and connection 87. The contacts 53 and 141 are 1ncircuit in each path for the periodic signahng current, and open whenthe wheel 139 is released upon turning in a fire alarm. Thus-no troublesignal from this transmitter can be sent until after the lire alarm boxis reset. Without this precaution, making of contacts 47 and 48 wouldresult in shorting relay 68, with attendant deener ization thereof. Thiswould cause the trou le signal to be given every time the fire alarm isoperated, even if there is no trouble.

I It may sometimes happen that the trouble signal at the lire stationwill remain unheeded during the Whole eriod of operation of the troublecode whee 75. In order to insure that some ,sort of a signal will stillbe active even after the spring motor 77 has run down, I provide ascheme for transmitting .a periodic si naling current continuously overtheclose re alarm circuit. For this purpose the relay 68 is providedwith a set of contacts 88 which are closed when this relay drops itsarmature. The closure of these contacts serves to connect the buzzer 89to a commercial alternating current source by the aid of connections 91and 92. This buzzer serves as an alarm near the scene of the trouble,but its main purpose is to affect a microphone or telephone transmitter90. The circuit for this telephone transmitter includes the primary coil7 9, the movable contact 65, the stationary contact 94, and a battery95. While the code wheel 75 is rotating, the contacts and 94 are open,so that the transmitter is incapable of affecting the iow of currentthrough the primary coil 79. However, when the-motor 77 has about rundown, an arm 93 carried thereby is arranged to operate the movablecontact 65 so as to connect it to the contact 94. The closing ofcontacts 65 and 94 serves to complete the circuit t'or the transmitter90 through the primary 7 9. At the same time, by appropriate stops forthe wheel 75, it is assured that the code wheel contacts 78 are open, sothat the main batteries 49 and 52 are rendered inactive. The periodicsignaling current paths are 'identical to those traced before; the soledif- Upon the occurrence of a lire the trouble loo ' sive to theperlo'dic signaling currents at the fire station. At this end,illustrated in Fig. 3, the condensers 96 and 97 are connected to thelines 29 and 30, and acgnnection 98 is provided between them, so as tof, place the two in parallel in the connection --99. This connectionleads toa relay 10'0,

whence the signaling current, which is transmitted through lines 29 and30 and condensers 96 and 97, passes through' connection 101, andappropriate signaling device 102, such as a telephone receiver, thedisconnecting snap switch 103, connection 104, to the ground 105. Thedevice 102 is thus actuated lin response. to the transmitted periodiccurrent signal. As soon as this signal is heeded, operation of device102 may be stop ed by actuating sna switch 103.

T e actuation of A. relay 100 by the si naling current causes theclosure of the re ay contacts 106, which serve to produce othersignaling indications by the aid of a 'commercial A. C. source, such asa lighting circuit. The relay contacts 106 are so arranged that they areclosed upon the reception of the first signaling impulse, and remainclosed thereafter until they are manually reset to open position. In#other words, the relay 100 merely serves to trip these contacts toclosed position, so as to energize other signaling devices continuously.The circuits for these other devices may be traced as follows: from themain 107 leading to the commercial source, blade 108 of a double poleswitch 109, a fuse 110, connection 111, contacts 106, to a point 112,where the circuit divides-one branch -including connection 113, asignaling device such as lamp 114, and lead 115 to the junction point116; the other branch includes a resistance 117, and lead 118 to thepoint 116; at this point the circuit reunites through the A. C. buzzer119, connection 120, fuse 121, and the other blade 122 of switch 109 tothe main 123. From this circuit it is evident that both the lamp 114 andbuzzer 119 are operated continuously on the occurrence of trouble andthat even if lamp 114 be inoperative or broken for any reason,

the buzzer would still be actuated due to the provision of the branchcircuit including the resistance 117.

The various alternate paths and signaling devices both at the receivingend and the transmitting end are provided for the evident purpose ofensuring that the signal will be transmitted and received. In additionto all these checks andsafety devices, I also preferably provide a` testcircuit for the main signal receiver 102, which will now be described.This test circuit may be traced as follows: from the positive right handterminal of the test battery 125 to a test ground 124, ground V105, lead104, switch 103, receiver 102, connection 101, relay 100, connections99, 98, and 1,28, relay 129,l adjustable resistance 127, and lead 126 tothe negative terminal of battery 125. This circuit is adjusted to have adefinite small amount of direct current/ flowingv through it, sutilcientto enable relay 129 to hold up its armature 130 and out of contact withthe contact 131. Should this test circuit be interrupted, as for exampleby a breakin any of the signaling connections, relay 129 would drop itsSli armature and complete the contact between v and connection 142 backto a tap point of battery 125.

There is a path from condensers 96 and 97 through relay 129, resistance127, battery 125 and ground 124 for the periodic signaling current, butthis path has much greater impedance than that including relay and thesignaling device 102; therefore no substantial signaling current willHow to interfere with the operation of the D. C. test circuit.

In order to isolate the various apparatus, the control relays 100 and131, together with resistances 117 and 127, may be housed in a commonbox or casing, as indicated by the dotted rectangle 136. Similarly thesignalingA devices and their switches may be housed in another casing,as indicated by the dotted rectangle 137.

A brief review of the operation of the system of Fig. 2 may now be setlforth. It there is no iire or trouble, the thermocouple circuit is inthe condition shown, the contact arm 45 being in neutral position, andtherefore operating magnet 38 is inoperative to move its armature 39.Upon the occurrence of a lire, the contact arm 45 swings to the left,and thereby causes actuation of relay 46, which in turn causes actuationof the operating magnet 38. The transmitting mechanism in the box 28 isthus rendered active, and direct current s-ignals are trans- 1transmitting end, the relay 68. would become inactive. Such trouble mayfor ex ample exist in the thermocouple circuit,

which would cause relay to release its.

armature and thus deenergize relay 68, or else the trouble may be in theconnections controlled by relay 46. The dropping of armature 74 of,relay 68 causes the trouble code wheel 77 to rotate, and also to setinto operation an induction coil for generating a. periodic signalingcurrent. The code wheel operates for a substantial eriod, during whichsignals are transmitte over the lines 29 and 30 in parallel, and throughthe condensers 82, 83, and 96 and 97, These signals operate the relay100 as well as the receiver 102. The relay 100 permits a lightingcurrent to operate, as additional signaling devices, thelamp 114 and thebuzzer 119. Inv

case these signaling impulses are perceived and steps taken to remedythe trouble, the signaling devices may be rendered inoperative byopening switch 103. Since this switch is also included in the local testcircuit, with battery and relay 129, the D. C. buzzer 134 will operatein response to the opening of the relay circuit, but by opening theswitch 133, the test circuit may be temporarily rendered inoperative, atleast until the trouble has been corrected at the transmitting point.

Should no heed be paid at the station to the trouble signal during theperiod of operation of code Wheel 7 5, the completion of movement ofthis Wheel will operate the contact 65 to connect the induction coilarrangement to a transmitter circuit for transmitting the sound from abuzzer 89 previously rendered active. A continuous periodic current isthereby transmitted, which is perceived at the station by the continuousoperation of the signaling device 102, and by the operation of devices114, and 119, caused by operation of contacts 106.

It is also to be noted that interruption ot the fire alarm circuit byturning in an alarm at any other tire alarm box will not interfere withthe transmission of the trouble signal, since under such circumstancesonly one of the two parallel paths for the trouble signal is interferedwith. Conversely, operation of the trouble signaling system will in noway interfere with the transmis-l sion of a tire alarm signal from anyone of thevtransmitter boxes 26.

In some of the following claims, the flow of current for operating thetransmitters is referred to as a flow of low frequency. This expressionis intended to cover the limiting condition of direct current ilow asdescribed specifically, since a direct current may be construed as onehaving zero frequency. The underlying thought of course is that twocurrents are used of widely differing frequency characteristics, andthis is true even when one of these currents is a direct current. V ,c

1 I claim:

1. In a fire alarm system, a lire alarm transmitter, a closed signalingcircuit controlled b the transmitter by varying the current owing inthecircuit, a circuit including means for increasing the current ilowwith the temperature, means operated in response to an increase incurrent flow 1n. said last circuit for operating the transmitter, meansresponsive to the interruption of the temperature responsive circuit fortransn'iitting a trouble signal over at least a portion of the signalingcircuit, whereinr only a portion of the )ath for the trouble signal isformed by the signaling circuit, and means for completing tlie path forthe trouble signaling current, said means being independent of theclosed circuit.

l 2. In a signaling system, a circuit, an induction coil having aprimary and a see ondary winding, a pair of means for sup plymg aperiodic current to the primary winding, means for connecting thesecondary winding to the circuit for transmitting a signal tliereovcr,one of said pair of means being capable only of limited operation, andmeans responsive to the completion of operation of said means forconnecting the other of said pair to the primary winding.

3. In a signaling system, a circuit, an induction coi. having a primaryand a sur ondary winding, means capable of a limited interval ofoperation for supplying a periodic current to the primary winding in aseries of intermittent periods, means for connecting the secondarywinding to the circuit for transmitting a signal thereover, anothermeans for supplying a periodic current to the primary continuously, andmeans responsive to the completion of the operation of the firstmentioned means, for connecting said other means to the primary winding.

4. In a signaling system, a circuit, an iuduction coil having a primaryand a sew ondary winding, a vibratory contact for the prin'iary winding,a source of direct current, a spring operated code wheel for completingthe primary circuit through the contact and the source, means forconnecting the secondary winding to the circuit for transmitting asignal thereover, a source ot periodic current, and means responsive tothe completion of operation of the code Wheel for connecting the sourceto the primary winding.

5. Inv a signaling system, a. closed direct current circuit, atransmitter for controlling the flow of current in the circuit, asignaling device responsive to the current variations in the circuitcaused by the transmitter, and means for transmitting a signalingperiodic current, comprising a transmitting device capable only of alimited period of operation, said transmittting device being adapted tosend impulses in a denite sequence, means for capacitively coupling saidtransmit-ting device to the circuit whereby a portion of the circuit isused to transmit the periodic current signals, means for completing thepath for these periodic current signals, Vsaid means being capacitivelycoupled to the circuit a't a point remote from the transmitting device,and includin a signal device 4responsive to the periodlc current, atelephone transmitter arranged to be substituted for the transmittingdevice upon completion of its operation, and a sound producing deviceaffecting the transmitter and adapted to be operated from a commercialsource of electrical energy.

6. In a tire alarm system, a closed direct current circuit, atransmitter responsive to temperature conditions for controlling theflow of current in the circuit, a signaling device responsive to thecurrent variations in the circuit caused by the transmitter, and meansresponsive to the occurrence of an in- Ioperative condition of thetransmitter for transmitting a signaling periodic current, comprising atransmitting device capable only of a limited period of operation, saidtransmitting device having means for sending impulses in a definite.sequence, means for capacitively coupling said transmitting device tothe circuit whereby a portion of the circuit is used to transmit theperiodic current signals, means for completing the path for theseperiodic current signals, said means being capacitively coupled to thecircuit at a point remote from the transmitting device, and including asignal device responsive to the periodic current, a telephonetransmitter arranged to be substituted for the transmitting device uponcompletion of its operation, and a sound producing device affecting thetransmitter and adapted to be operated from a commercial source ofelec,- trical energy.

7. In a signaling system, a circuit, an induction coil having a primaryand a secondary Winding, means for supplying a periodic current to theprimary Winding` said means being capable only of limited operation,means for connecting th-e secondary winding to the circuit fortransm1tt1ng a signalthereover, a telephone transmitter,

.a source of current' for the transmitter,

means responsive to the completion of operavtion of said periodiccurrent supplying means, for connecting the telephone transmitter andits source to the primary wmdlng, and a sound produclng device affectingthe telephone transmitter and adapted to y ondary Winding, means capableof a limited interval of operation for supplying a periodic current tothe primary Winding inca series of intermittent periods, means for con?necting the secondary Winding to the circuit 4for transmitting a signalthereover, atelcphone transmitter, a source of current for thetransmitter, means responsive to the completion of the operation of theperiodic current `supplying means, for connecting said telephonetransmitter and its source to the primary Winding, and a sound producingdevice adapted to be operated from a commercial source of electricalenergy and affecting the telephone transmitter.

9. In a signaling system, a circuit, an induction coil having a primaryand a. secondary Winding, a vibratory contact for the primary Winding, asource of direct current, a spring operated code Wheel for completingthe primary circuit through the contact and the source, means forconnecting the secondary Winding to the circuitfor transmitting a signalthereover, a telephone transmitter, a source of current for thetelephone transmitter, means responsive to the completion of theoperation of the code wheel for connecting the telephone transmitter andits source of current to the primary Winding, and a sound producingdevice adapted to be operated from a commercial source of electricalenergy and affecting the telephone transmitter. p

In testimony whereof, I have hereunto set my hand.

THOMAS A. MOLLARD.

